A trend of a handheld electronic device such as a smart phone is that its touch screen is getting larger and larger, whereby a keypad, particularly a dial pad, thereof can be getting larger and larger. To enable a user to conveniently operate the keypad, a single hand-operated keypad is equipped whereby the user can input information into the handheld electronic device. The single hand-operated keypad is a reduced version of the normal keypad and located selectively near one of two lateral sides of the handheld electronic device when it is shown on the touch screen.
Such a single hand-operated keypad in some measure can help the user to operate the handheld electronic device more conveniently. Nevertheless, a size of the single hand-operated keypad is fixed, whereby its usefulness is limited. The single hand-operated keypad cannot be adapted to different users having different palm sizes.